The field of this invention is that of pressure sensors and the invention relates more particularly to a cylinder pressure transmitter responsive to variations in pressure within a cylinder of an internal combustion engine to provide control signals for use in regulating engine operation.
In commonly assigned, copending patent applications Ser. Nos. 561,842 and 561,757 filed Dec. 15, 1983, cylinder pressure transmitters are shown to comprise a body mounting pressure responsive piezoelectric means in sealed relation to an engine cylinder to be responsive to variations in cylinder pressure during engine operation to provide initial electrical signals representative of pressure variations in the cylinder. Those transmitters include metal diaphragms which shield the piezoelectric means from the cylinder environments while transmitting pressure forces from the cylinders to the piezoelectric means for generating the desired pressure responsive signals. High temperature electronic means are carried and electromagnetically shielded on the mounting body of the device for amplifying the signals provided by the piezoelectric means to provide low impedance signals for transmission to computer control or other signal processing means at a location remote from the engine cylinder for regulating engine operation to improve performance. However such cylinder pressure transmitters are somewhat difficult to manufacture at low cost with uniform properties and high reliability and the piezoelectric means tend to be subjected to undesirably high temperatures due to heat-transfer from the engine cylinder environment through the diaphragm. The transmitters are also subjected to heavy vibrations during use so that of electrical connection reliability is of concern. Reference is also made to the commonly assigned copending applications Ser. Nos. 665,426, 665,490 and 665,237 filed of even date herewith.